var arr = [3, -15, -1, 2, 3, 4, 2, -1, 2];

var lengthOfSequence = 1;
var bestStartPositionOfSequence = 0;
var bestLengthOfSequence = 1;

for (var i = 1; i < arr.length; i++)
{
    if (arr[i] > arr[i - 1])
    {
        lengthOfSequence++;

        if (lengthOfSequence > bestLengthOfSequence)
        {
            bestLengthOfSequence = lengthOfSequence;
            bestStartPositionOfSequence = (i - (bestLengthOfSequence - 1));
        }
    }
    else
    {
        lengthOfSequence = 1;
    }
}

for (var i = bestStartPositionOfSequence; i < (bestStartPositionOfSequence + bestLengthOfSequence); i++)
{
    console.log(arr[i]);
}